Magnet roller developing device and image forming apparatus for reducing obstructions in developer circulation path

A developing device, comprising:

• a developing roller having a magnet roller configured to transport developer to be used in developing an electrostatic latent image;
• a regulating member configured to regulate an amount of the developer transported to the electrostatic latent image with the development roller;
• a reflux plate configured to reflux excess developer regulated by the regulating member away from the regulating member;
• and
• a rubbing member arranged to face the developing roller at a second gap which is larger than a first gap defined by the developing roller and the regulating member, wherein the rubbing member is configured to rub developer transported to the first gap, in order to create friction prior to preliminary electrification of the developer;
• and
• wherein the magnet roller has a plurality of magnetic poles arranged in circumferential direction thereof and one of the magnetic poles is provided so that the magnetic pole faces the second gaps and a polar central axis thereof corresponds to a minimum position of the second gap;
• and
• wherein the second gap G2 (mm) G1<G2≦0.8×Dm, where G1 is the first gap (mm) and Dm is a width of magnetic pole (mm).

A developing device, comprising:

• a developing roller having a magnet roller configured to transport developer to be used in developing an electrostatic latent image;
• a regulating member configured to regulate an amount of the developer transported to the electrostatic latent image with the development roller;
• a reflux plate configured to reflux excess developer regulated by the regulating member away from the regulating member;
• and
• a rubbing member arranged to face the developing roller at a second gap which is larger than a first gap defined by the developing roller and the regulating member, wherein the rubbing member is configured to rub developer transported to the first gap in order to create friction prior to preliminary electrification of the developer;
• and
• wherein the magnet roller has a plurality of magnetic poles arranged in circumferential direction thereof and one of the magnetic poles is provided so that the magnetic pole faces the second gap and a polar central axis thereof is located between a position corresponding to the minimum position of the second gap and a position displaced 1.5 degree upstream from the minimum position of the second gap in a direction of developer developer transportation;
• and
• wherein the second gap G2 (mm) is defined as G1<G2≦0.8×Dm, where G1 is the first gap (mm) and Dm is a width of magnetic pole (mm).